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Engine RPM is high, car is not accelerating

Discussion in 'Gen 2 Prius Technical Discussion' started by F8L, Mar 28, 2011.

  1. F8L

    F8L Protecting Habitat & AG Lands

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    I know we have discussed this in a previous thread but because I got a picture of the car doing this today, I thought it would be a good thread topic. :)

    The Situation:
    Traveling downhill, with no throttle input. The car is regenerating power as I coast down the hill. I hear the engine turn on and rev up. I glance at the Scangauge and see RPM is at 3045 or so. MPG is still 9999 and SOC is 77.something.

    I grab my cell phone, turn off my geology audio book and snap a picture of the SG2. By this time the RPM was dropping but I caught it before it came all the way down and MPG was still 9999. The RPM stayed around 1600 or so until SOC dropped below 70%.

    TheCar received no throttle input the entire time nor did the car accelerate. I found it rather cool that it could rev so high and use no fuel.
     

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    #1 F8L, Mar 28, 2011
  2. cwerdna

    cwerdna Senior Member

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    I don't bother monitoring the SG's MPG or GPM figures... but yeah, I hit the car putting itself in B mode pretty often where I live now: coasting <42 mph downhill, ICE at 0 rpm, soc up pretty high, in the 75%+ range, then ICE suddenly kicking on and sometimes going pretty high.
     
    #2 cwerdna, Mar 28, 2011
  3. seilerts

    seilerts Battery Curmudgeon

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    You two should put in an EV mode switch. Why not put that power to the wheels instead of dispersing it into engine drag?
     
    #3 seilerts, Mar 28, 2011
  4. F8L

    F8L Protecting Habitat & AG Lands

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    I keep the SG mpg on so I can leave the MFD screen on consumption. Keeps my eyes on the road. :)

    So in this case is the engine just being spun up via electric energy just to bleed off excess regen?

    I have and EV switch. It doesn't help me on these roads though. It's a very winding rural highway and nearly all downhill until I get to town. I can usually just use hypermiling techniques to keep the engine off for so long that it fires up because the coolant temp has dropped too low. Did you have a specfic scenario in mind where the EV switch could help me?
     
    #4 F8L, Mar 28, 2011
  5. SageBrush

    SageBrush Senior Member

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    Excess battery SOC I think. I am pretty sure what you experienced only happens when the battery is full.
     
    #5 SageBrush, Mar 28, 2011
  6. F8L

    F8L Protecting Habitat & AG Lands

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    Aye, the only times I've noticed it is when I'm going downhill and regenerating a lot of energy that I cannot use (no long stretches I can glide or use EV).
     
    #6 F8L, Mar 29, 2011
  7. mikewithaprius

    mikewithaprius New Member

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    On the one descent in my various drives where I purposely try to get full SOC, I have to try to time it so that I only get full green right at the end of the hill. If I charge up too quickly on the hill and have more downhill to cover, the engine starts up like this and wastes the energy I was just about to use :eek:
     
    #7 mikewithaprius, Mar 29, 2011
  8. mikewithaprius

    mikewithaprius New Member

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    F8L, do you use a neutral glide if under 42? Could save the charge that way and can brake without more regen. Clean the rust off the rotors, too!
     
    #8 mikewithaprius, Mar 29, 2011
  9. dogfriend

    dogfriend Human - Animal Hybrid

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    Yes. I've had this happen, but only after a lot of regen.
     
    #9 dogfriend, Mar 29, 2011
  10. V8Cobrakid

    V8Cobrakid Green Handyman

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    have you ever played around with the PSD animation?

    it's for the gen1.. but it's still relevant to the new prius... to an extent... (basic form)
     
    #10 V8Cobrakid, Mar 29, 2011
  11. uart

    uart Senior Member

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    Hi F8L, was the SOC indicator showing 8 green bars when this happened?

    Same here Mike. I find that once I get eight green bars on the SOC display that I can only regenerate just a little bit more before it triggers the dumping of excess charge.
     
    #11 uart, Mar 29, 2011
  12. F8L

    F8L Protecting Habitat & AG Lands

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    I could but there are only a few sections that I can glide in for more than 10seconds before I pick up too much speed and have to brake before entering a curve. If I were to use a neutral glide I could keep most of the energy I have regenerated, not induce an energy dump despite my braking, then use that energy on a different stretch of road?

    I have not but I will now. Thanks for the link. :)

    I cannot say. I did not glance at that screen but having traveled that road so many times over the last 5 years and seeing 8 green bars I would place a high wager that it was full. The SG2 SOC read 77.x% (it may have been higher right before the engine rev'd up). I was stuck behind a couple of other cars who were not taking corners as fast as I usually do so I was doing a lot of braking and just lifting off the throttle and letting regen slow me down. This usually generates a lot of energy on this road.
     
    #12 F8L, Mar 29, 2011
  13. mikewithaprius

    mikewithaprius New Member

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    Exactly! The braking will feel different, and you might even hear a little squealing of the brakes. An odd sensation, I forgot I had friction brakes when I first did that haha

    If I'm at an all-green or near all-green state and need to save it, I might use neutral to brake, and then go into drive to drive for a second if acceleration is needed for whatever reason, back into neutral, etc. It's so quick on the Prius it's not really a hassle. I keep my hand on the knob so I don't forget about the "gear", too.
     
    #13 mikewithaprius, Mar 29, 2011
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  14. F8L

    F8L Protecting Habitat & AG Lands

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    That makes sense. I can play around with it and learn which spots this technique would work best in. Thanks for the tips guys. :)
     
    #14 F8L, Mar 29, 2011
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